This invention relates to a packaging container of cardboard, paper or the like for liquids, the container being rendered impermeable by at least an internal plastic coating and having, at least at one end, a double thickness portion, the interior of which communicates with the interior of the container, the wall of said portion being provided with a seizable strip of cardboard.
It is known that milk, juices and water are at present available commercially in containers of this kind. These known containers are polyhedral in shape and more particularly are parallelepipeds, tetrahedrons, or cubes.
Production methods vary. One very practical way of producing such a container is to form a tube, flatten it, fill it, seal it transversely, or separate it from the tube. Containers of this kind have seams in two opposite lateral walls and one end-wall, or in two opposite end-walls and one lateral wall, in the form of double cardboard strips with a sealed seam which can be bent up and gripped.
Whether they are used for powdered and granular material, or for liquids, all packaging containers are faced with the problems of proper sealing and easy opening when it is desired to empty them. In this connection, a wide variety of opening means have been developed and are already known. One example is a known rectangular container having double-thickness triangular flaps formed on its opposite end-walls, the interior thereof communicating with the interior of the container. A double strip of cardboard with a sealing seam extends to the outer tip of the triangular flaps which, in the final shape of the container, are folded about an edge-line between one narrow lateral wall and one end-wall, and which are secured thereto by spot-sealing. In some designs of this known container, the opening means provided is in the form of a perforation-line, closed per se, and rectangular in plan view, located in the upper end-wall and extending downwardly for a short distance above the edge-line in the triangular flaps. Sealing is improved by welding a plastic cover-strip internally, at a certain distance from the perforation-line. Located within the perforation line, the projection of which is rectangular in plan view, in the vicinity of the edge-line, is a large weld-spot and, at a distance therefrom at the end remote from the edge-line, at least one other, smaller, weld-spot to which the plastic-coated strip of carrier-material, with the internally applied plastic cover-strip, is welded. This makes it possible, upon tearing off the strip of plastic formed by the closed perforation-line, to expose holes, within the area of the tear-off cardboard strip, the larger front opening being used as a pouring spout, while the one or two smaller rear openings are used as air-inlets. This provides a highly satisfactory opening means for a rectangular container which is fluid-tight and can be opened relatively easily (German Patent Application P 25 20 569.0-27).